Moisture resistant friction elements and process of producting same



Patented Apr. 21, 1953 MOISTURE RESISTANT FRICTION ELE- MENTS AND PROCESS OF PRODUCING SAME Edward M. Daley, Springfield, Mass., assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application September 21, 1948, Serial No. 50,439

4 Claims.

This invention relates to friction elements for match containers. More particularly, the invention relates to friction elements for match containers which are impervious to moisture and especially to high humidities.

- The common variety of safety matches which aresold either in boxes or in cardboard folders must be struck against a friction element containing red phosphorus or other igniter in order to'start them burning. A. constant source of irritation to users of safety matches has been the failure of the friction element due to the absorption of moisture either due to contact with water or to the influence of highly humid conditions. When moist, the components of the friction elements rub off when attempts are made to strike a match, and the match does not light.

It is an object of this invention to provide an improved friction element for safety matches.

A further object is to provide a friction element for safety matches which is substantially impervious to water.

A further object is to provide a binder for friction elements used to light safety matches which renders the friction element impervious to moisture.

These and other objects are attained by using a styrene polymer or copolymer emulsion as a binding agent for the igniting components of friction elements.

The following examples are given in illustration and are not intended as limitations of the scope of this invention. Where partsare mentioned, they are parts by weight.

Example I 100 parts of friction grits containing'amorphous phosphorus, antimony and ground glass were mixed into '75 parts of anaqueous emulsion of polystyrene to obtain a thick aqueous paste. The paste was coated on a strip of cardboard and allowed to dry at about 60-90 C. After it was thoroughly dried, it served as an efficient igniting element for safety matches. The dried strip was then placed in a stream of cold water. It was then tested as an igniting means while wet by striking twenty matches on the wet coating in rapid succession. All of the matches ignited immediately, and there was no evidence of substantial separation of the friction material from the cardboard. A second strip carrying a dried coating made as described above was subjected to an atmosphere containing about 90% relative humidity at C. for four hours.

It was then removed from the conditioning I chamber and immediately tested as an ignition means. Again all matches lit without difficulty and there was no evidence of separation of the friction material from the cardboard.

In contrast, a standard friction element when moistened with a little water failed to light a match, and light rubbing with little pressure served to remove substantially all of the friction material from the cardboard.

When the amount of the styrene emulsion was increased to 125 parts, similar results were obtained except the coating paste was somewhat thinner resulting in a thinner coating on the cardboard. When the amount of styrene emulsion was reduced to parts, a very thick paste was obtained which gave a thick coating of friction material. In this case, it was found advantageous to thin the paste with water to obtain an optimum consistency for the coating material. However, the amount of polystyrene present was sufiicient to serve as an, emcient, permanent, and substantially water-impervious binder for the friction grits.

The polystyrene emulsion used in the example contained 40% solids by weight of which was polymerized styrene and was a plasticizer, butyl benzyl phthalate. The emulsion was prepared by polymerizing monomeric styrene in aqueous emulsion in the presence of potassium persulfate as a catalyst and ammonium oleate as the emulsifying agent. The plasticizer was incorporated in the emulsion prior to the polymerization step.

Other plasticizers may be used to flexiblize the polystyrene bond and prevent the friction elements made therewith from cracking under rough usage. Among the plasticizers which may be used are the dialkyl phthalates such as diethyl phthalate, dimethyl phthalate, dibutyl phthalate, alkyl phthalyl alkyl glycollates such as butyl phthalyl butyl glycollate, chlorinated diphenyls, chlorinated terphenyls, triaryl phosphates and other Well-known ester plasticizers. The amount of plasticizer may be varied from about 15 parts to about parts per 100 parts of polystyrene. The plasticizer may be incorporated in the emulsion after the polymerization process has been completed, during the course of the polymerization, but preferably before the polymerization is started.

The polystyrene emulsions may be modified by the addition of from 1 to 100 parts, per 100 parts of polystyrene, of a protective colloid such as proteins including casein, zein, etc., salts of styrene-maleic anhydride copolymers, ammo- 3 nium alginates, methyl celluloses, etc. The protective colloids serve to improve the coating properties of the emulsion so that a more even coating of the friction grits on the cardboard is obtained.

Ezcample II 100 parts of friction grits were mixed with parts of a polystyrene emulsion which contained 6 parts of polystyrene and 4 parts of butyl benzyl phthalate. To this mixture, 10 parts of ammonium caseinate were added with constant agitation until a' smooth, free-flowing paste was obtained. The paste was coated on a cardboard and dried. The dried coating served as an eflicient ignition medium for safety matches before and after immersion in water or exposure to relative high humidities. This result is particularly surprising in View of the well-known far as adhesion to the various surfaces is con- I cerned, but the water sensitivity of the coatings increases'rapidly as the amount of polystyrene is decreased below 40%.

The friction grits used in the examples comprised mixtures of amorphous phosphorus, antimony and ground glass. These are conventional grits and may be varied as desired to obtain various ignition qualities.

Polystyrene is the preferred resin ingredient of the adhesives of this invention. It may, however, be substituted in part or in whole by polymers of styrene substituted on the ring or in the side chain by aliphatic groups or styrene substituted in the ring by halides. Examples of such substituted styrenes are alpha-methyl styrene, alpha-ethyl styrene, m-, o-, and p-methyl styrenes, o,p-dimethyl' styrene, alpha-methyl pmethyl styrene, p-ethyl styrene, monochlor styrenes, dichlorstyrenes, monofiuor styrenes, difluor styrenes, etc. Furthermore, copolymers of styrene and substituted styrenes with one another or with other unsaturated compounds copolymerizable therewith may be used provided that styrene or substituted styrene constitutes a major part of the copolymer. Thus styrene may be copolymerized with alpha-methyl styrene, dich1or-' styrenes, acrylic acid esters, alpha-substituted acrylic acid esters, unsaturated nitrilessuch as acrylonitrile, fumaronitrile, etc., dienes such as butadiene, isoprene, dimethyl butadiene, piperylene, etc., and the products used as the adhesives in this invention.

In the preferred embodiment of this invention, the polystyrene is used in the form of an aqueous emulsion, but it is within the scope of the invention to use the polystyrene or its copolymers in the form of a hot melt composition or i a solution in organic solvents. In either case, it is a simple matter to incorporate th frictional grits in the adhesive medium and to coat the composition on cardboard, wood, paper, or other porous and their containers are exposed to water.

4 medium. The coating compositions adhere well to such porous surface and are substantially impervious to moisture even though the porous surfaces themselves absorb water readily.

Friction elements made'according to this invention will permit match books, folders, packs, boxes, etc., coated therewith to be exposed to conditions of moisture which have hitherto rendered them useless. They are especially useful to campers, hunters, trappers, etc., who otherwise must carry matches in waterproof pouches and guard them carefully in the event of a heavy rainstorm or of an accident wherein the matches They are also especially useful in climates where high relative humidities' frequently occur since, even though the container itself might absorb much water, the friction element will remain dry and act fliciently to ignite matches.

It is obvious that many variations may be made in the products and processes of thi invention without departing from the spirit and scope thereof as defined in the appended claims.

What is claimed is:

1. Substantially Water impervious friction strips for igniting safety matches comprising plasticized polystyrene and an ignition material, said ignition material being incorporated in the plasticized polystyrene.

2. Substantially water imperviou friction strips for igniting safety matches comprising an ignition material and a copolymer of styrene with a coplymerizable monomeric substance, the styrene constituting a major part of the copolymer, said ignition material being incorporated in the copolymer. V

3. A process for preparing substantially waterim-pervious friction strips for igniting safety matches which comprises mixing ignition material with an aqueous emulsion of plasticized polystyrene, coating the mixture on a, porous surface, and drying the coating.

4. A process for preparing substantially water impervious friction strip for igniting safety matches which comprises mixing ignition mate rial with an aqueous emulsion of a plasticized co polymer of polystyrene, said copolymercontaining a major proportion of styrene, coating the mixture on a porous surface and drying the coat- EDWARD M. DALEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,529,322 Schapiro Mar. 10, 1925 1,640,224 Robinson Aug. 23, 1927 2,004,436 Jaeger June 11, 1935 2,030,892 Pelipetz Feb. 18, 1936 2,128,368 Larsson Aug. '30, 1938 2,361,019 Gerhart Oct. 24, 1944 2,375,701 Smith May 8, 1945 2,389,552 Sanford Nov. 20, 1945 2,468,027 Britten Apr. 26, 1949 FOREIGN PATENTS Number Country Date 314,852 Great Britain Nov. 28, 1929 404,298 Great Britain Jan. 8, 1934 558,317 Great Britain Dec. 31, 1943 

1. SUBSTANTIALLY WATER - IMPERVIOUS FRICTION STRIPS FOR IGNITING SAFETY MATCHES COMPRISING PLASTICIZED POLYSTYRENE AND AN IGNITION MATERIAL, SAID IGNITION MATERIAL BEING INCORPORATED IN THE PLASTICIZED POLYSTYRENE.
 3. A PROCESS FOR PREPARING SUBSTANTIALLY WATERIMPERVIOUS FRICTION STRIPS FOR IGNITING SAFETY MATCHES WHICH COMPRISES MIXING IGNITION MATERIAL WITH AN AQUEOUS EMULSION OF PLASTICIZED POLYSTYRENE, COATING THE MIXTURE ON A POROUS SURFACE, AND DRYING THE COATING. 